1. Field of the Invention
The present invention relates to a cable telephony terminal equipment (i.e., device) that concurrently uses a telephone line directed toward a cable television network and a telephone line directed toward a public switched telephone network (hereinafter referred to also as "a PSTN").
2. Description of the Related Art
In recent years, as telecommunications and broadcasting have become more integrated, the CATV (cable television) enterprise has also progressed from a conventional stage that mainly comprised broadcasting services of distributing images or the like to a new stage that also comprises telecommunication services. Particularly, the current status is that the construction of a so-called "cable telephony system" of utilizing the cable television network as a telephone subscriber's network has proceeded as means for a second telephone service in addition to the first telephone service that stands on the use of the PSTN network.
In this cable telephony system, the line branched from the telephone line for the cable television network (hereinafter referred to as "the cable telephony line") (for example, a coaxial cable or optical fiber) is installed within each subscriber home in addition to the conventionally installed telephone line for the public switched telephone network (hereinafter referred to as "the PSTN line"). For this reason, telephones that are connected to the PSTN line and the cable telephony line respectively are both installed within the subscriber home.
In this CATV telephone, the subscribers that belong to the same cable television network can have a telephone conversation through the use of the cable television network. Also, by connecting this cable television network to the public switched telephone network in charge of a first-class telecommunication enterpriser (regulated by Japan Telecommunication Enterprise Law), the CATV telephone can communicate with a subscriber of the public switched telephone network (PSTN) or an international network.
However, the above-mentioned CATV telephone system has the problem that because the PSTN telephone and the cable telephony are individually separately installed within the subscriber home, at the time of incoming call (reception) the user must make his judgement of which telephone the incoming call is on and so this judgement becomes complex.
Also, when using the telephone, a general user in many cases makes the line selection according to the use charges. However, in a case where the two telephone systems (one for the PSTN and the other for the cable television network) are used, because the charge systems therefor are complex, there is the problem that the selecting criterion is difficult for the user to understand and therefore the user becomes annoyed with his judgement of which telephone he should use each time he makes his telephone call.